The present invention relates to the field of coupling devices for joining elongated structural elements together.
The patent to Leuthy et al. U.S. Pat. No. 3,234,603 illustrates a typical prior art method of butt splicing horizontally oriented reinforcing steel bars in the field. A crucible for containing exothermic powder is clamped to a mold structure containing the elongated structural members by means of a clamping device. An exothermic reaction is thereafter produced in the crucible, and molten iron flows by gravity down into the mold cavity wherein it is solidified. The crucible and its associated clamping device must be thereafter removed and any sprues must be cut off. In other words, this technique causes molten metal to be produced in a separate external crucible and introduced into a mold cavity. See also U.S. Pat. No. 3,255,498 also to Leuthy et al. illustrating a somewhat different device for welding vertical oriented reinforcing bars.
Although the above-described method has been used for many years in the field, for butt splicing reinforcing bars, it suffers from numerous drawbacks. The powdered exothermic material is usually measured and mixed in the crucible after the crucible is clamped to the mold described hereinabove by means of relatively elaborate clamping devices. After the splicing process is completed, the crucible must be thereafter unclamped and removed from the reinforcing bars along with the mold. These crucibles are relatively expensive, costing in the neighborhood of $50.00 apiece and are subject to breakage. In addition, the time required to charge the crucible, clamp it to the mold, unclamp it, and clean it between uses, is wasteful in terms of labor. The above-mentioned disadvantages have been eliminated by virtue of the present invention as the invention does not require an external crucible, a crucible clamping device, or a mold. Furthermore, the above-mentioned measuring and mixing of exothermic material in the crucible is eliminated together with the safety hazard due to sparks and smoke produced at upper portions of the crucible. Also, the same coupler may be employed regardless of the orientation of the reinforcing bars to be joined, since it uses a propellant and functions independently of gravity. In summary, it is desirable to provide a rapidly actuated and laborsaving coupling device which is far less costly to use than the above-mentioned devices and results in greater safety together with the elimination of crucibles, different types of crucible clamping devices, and molds.